A number of apparatuses for underwater breathing are known in the prior art. One of the most familiar is the system commonly known as scuba, comprising a high pressure tank worn by the diver who breathes through a mouthpiece having a regulator for reducing the air pressure to a breathable level. This apparatus works very well for its intended purpose, but requires special training in order for a diver to become competent in its use. In addition, the high pressure needed for the tanks presents an added risk, and also requires special equipment to refill the tanks. Further, the high pressure air necessitates the use of a complicated and often expensive regulator to reduce the pressure to a breathable level for the diver. Basic scuba apparatus is described in U.S. Pat. No. 829,274 to Knoff.
Another familiar apparatus for use in underwater breathing by a diver is the widely used snorkel. This apparatus also works very well for its intended purpose, but allows only a very shallow operation without some type of pump to force air to the diver. Variations of the snorkel may be seen in U.S. Pat. No. 835,950 to Iwanami; U.S. Pat. No. 4,583,536 to Jan; and U.S. Pat. No. 3,525,335 to Freeman.
A third type of underwater breathing apparatus comprises a pump situated on the surface of the water and delivering air through an air line to a submerged diver. Apparatuses of this type are particularly useful for diving for extended periods of time. However, devices utilizing this principle require constant pumping to avoid air being delivered to a diver in pulses. For this reason, a heavy duty electric or gas-powered pump is typically used in this type of system. In addition, regulators are typically necessary to control the air pressure delivered for breathing by the diver. Examples of this type of invention may be seen in U.S. Pat. No. 813,431 to Iwanami and Woodward; U.S. Pat. No. 3,467,091 to Aragoma; and U.S. Pat. No. 4,674,493 to Mitchell.
In addition to underwater breathing apparatuses, a number of apparatuses used for breathing in irrespirable environments are known. For example, the apparatus disclosed by Great Britain Patent No. 19,080 consists of a manual pump, a breathing bag, and a helmet or mask all connected by flexible tube. Air is delivered to the breathing bag by the manual pump and is then forced to the helmet or mask for respiration by the individual. Although the pressure at which air is forced to the mask is not disclosed, it is unlikely that it is above atmospheric pressure. Great Britain Patent No. 436,546, discloses an apparatus and method for providing breathable air to individuals at high altitudes, especially for use in an airplane. The air supply is compressed to a pressure corresponding to air at ground level and may be supplied to an intermediate rigid container or reservoir, in which air may be stored at an elevated pressure. The air is then supplied to an individual wearing a helmet via a flexible tube or to a chamber in which the individual resides. The pressure at which the air is delivered to the helmet or chamber is kept substantially the same (i.e., ground level pressure) at all altitudes. Neither of the Great Britain patents addresses the unique problems involved in supplying air to underwater divers.